ML20196D734

Third Quarter 1998 & Oct 1998 Data Rept for Prairie Island Isfsi

ML20196D734
Person / Time
Site:	Prairie Island
Issue date:	11/20/1998
From:	MINNESOTA, STATE OF
To:
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ML20196D707	List: ML20196D705 ML20196D734
References
NUDOCS 9812020319
Download: ML20196D734 (15)

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Prairie IslandNuclear Generating Plant and Independent Spent Fhel Storage ;

y n ~-A q g Introduction This report provides data on radiation levels surrounding Northern States Power Company's (NSP) Independent Spent Fuel Storage Installation (ISFSI) at the Prairie ,

Island Nuclear Generating Plant. The report covers the Third Quarter of 1998 and October 1998. Monitoring of the ISFSI is.done with thermoluminescent dosimeters (TLD) and pressurized ionization chambers (PIC). The report contains data gathered in accordance with agreements between NSP and the Minnesota Department of Health (MDH).

Currently, seven casks are storing spent fuel inside the ISFSI.

Beginning in the last quarter of 1995, MDH environmental dosimeters began detecting neutrons outside the ISFSI but on NSP property. An estimate of neutron levels at the distance of the nearest resident indicates that neutron plus gamma radiation is less than the 0.054 mrem per year condition of the Certificate of Need issued by the Public Utilities Commission. Further details are provided in the Analysis and Comments section of this ~

report.

TLD Gamma Monitorine TLD are small semiconductors that respond to ionizing radiation by trapping electrons in

" forbidden" regions. When they are heated, they emit light that is proportional to the amount of radiation received. Only the total amount of radiation absorbed is recorded; it is not possible to estimate when the radiation was absorbed (that is, distinct hourly radiation levels are not available). MDH uses the Panasonic TLD system.

TLD were exposed from June 29 to,1998, during the Second Quarter of 1998. MDH places 12 pairs of TLD around the plant and ISFSI. They are located from Hastings  !

(which functions as a control because it is 12 miles upwind and unlikely to experience i radiation from the plant), to Welch and to Red Wing. A more detailed description of the locations is given in Table 1. l Average values for gamma exposure rates (milli Roentgen per 91 day quarter) are presented in Table 2 for each location by quarter. Also, included are the previous eight annual averages of the 32 quarters between January 1989 and December 1997.

Beginning in 1993, the Department began background monitoring at the ISFSI in

~

anticipation of dry cask storage in 1995 by adding five new TLD locations specifically to monitor the ISFSI. A sixth TLD location was added in 1996.

Pressurized Tonization Chamber (PIC) Monitorine During this reporting period, daily radiation data were collected by the PIC system, which was installed in January 1995. The system consists of two Ion chambers, computer 9812020319 981120 f PDR ADOCK 05000282 g Y PDR L

memories and modems that are accessed every 20 minutes by Health Department computers in St. Paul. The computers automatically page and call Health Department staff

.if unusual radiation levels are detected. One chamber is located about 100 feet north of the ensks and the other is located about 100 feet south, i

Table !. MDH TLD Locations Descriotio_n Location Descrintion NSP Code i

Nearest Resident Nearest residence to reactors; about 0.5 miles SSE P-02S j Northwest Sector Intersection of Wakonade Dr. and Sturgeon Lk Rd. None l Lock and Dam No. 3 At end of Wakonade Drive None Mount Carmel Road At end of Mount Carmel Rd. . P-03S j Red Wing Intersection of Hwy 61 and Old Main St. None Hastings (Control) Hwy 61 near Hastings Ford dealer None ISFSI #1(Outside Berm) Centered about 400 feet N of berm P-011B ISFSI #2 (Outside Berm Centered about 400 feet S of berm None ,

ISFSI #3 (Inside Berm) Centered about 310 feet W of pad center P-021X - l ISFSI #4 (Inside Berm) Centered about 360 feet E of pad center P-02IA ISFSI #5 (PI Community) NE corner of intersection of new plant rd and RR None' l ISFSI #6 (NSP Trn. Center) Wakonade Drive at Training Center None l

Table 2. Averaee Gamma Exoosure Rates Near Prairie Island. 1989-1998 Location -------------------------- m R/Q u a rt e r--- -------------------

1989-1997 1st 098 2nd 098 3rd 098 4th 098 Nearest Resident 15.2 14.0 13.0 14.0 Northwest Sector 12.9 11.6 11.5 12.5 Lock and Dam No. 3 13.6 12.6 12.6 11.6 Mount Carmel Road 15.4 13.3 11.7 13,3 Red Wing 15.1 12.8 11.9 14.1 Hastings (Control) 14.7 12.6 13.7 13.9 1993-1994 ISFSI #1(Outside Berm) 15.1 16.5 15.4 16.3 ISFSI #2 (Outside Berm) 15.5 14.5 16.5 16.9 ISFSI #3 (Inside Berm) 15.0 22.8 24.1 22.6 ISFSI #4 (Inside Berm) 15.9 18.5 16.8 18.1 ISFSI #5 (PI Community) 15.3 12.1 13.8 13.3 ISFSI #6 (NSP Trn. Center) 14.6 14.6 13.3 14.0 Locations of both PIC are presented in Figure 1. Also shown are the locations of the seven spent fuel casks.

Hourly gamma data were collected from October 1 to October 31,1998, and are summarized in Table 3 for PIC No. I and in Table 4 for PIC No. 2 (daily averages are presented- even though data for every five minutes are available).

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Table 3. October 1998 Data Report for PIC No. 1 I

strrt start End End Ave. Dose Interval Intervat Standard Interva'. Date  %

l D:ta Time Date Time Dose Rate Max Min Dev. Time Recovered Recovered j 10/01/98 00:00:00AM 10/02/98 00:00:00AM 1.720mR 71.7uR/h 72.5uR/h 70.7uR/h 0.4uR/h 001-00:00 001-00:00 100.0 10/02/98 00:00:00AM 10/03/98 00:00:00AM 1.724mR 71.8uR/h 72.7uR/h 71.0uR/h 0.4uR/h 001 00:00 001-00:00 100.0 10/03/98 00:00:00AM 10/04/98 00:00:00AM 1.718mR 71.6uR/h 72.8uR/h 70.8uR/h 0.3uR/h 001 00:00 001-00:00 100.0 10/04/98 00:00:00AM 10/05/98 00:00:00AM 1.716mR 71.5uR/h 73.3uR/h 70.9uR/h 0.3uR/h 001-00:00 001-00:00 100.0 10/05/98 00:00:00AM 10/06/98 00:00:00AM 1.733d 72.2uR/h 73.9uR/h 71.3uR/h 0.6uR/h 001-00:00 001 00:00 100.0 10/06/98 00:00:00AM 10/07/98 00:00:00AM 1.724mR 71.9uR/h 72.6uR/h 71.1uR/h 0.2uR/h 001 00:00 001 00:00 100.0 10/07/98 00:00:00AM 10/08/98 00:00:00AM 1.719mR 71.6uR/h 72.8uR/h 71.0uR/h 0.3uR/h 001-00:00 001 00:00 100.0 10/08/98 00:00:00AM 10/09/98 00:00:00AM 1.722d 71.8uR/h 73.0uR/h 70.7uR/h 0.6uR/h 001-00:00 001-00:00 100.0 1 10/09/98 00:00:00AM. 10/10/98 00:00:00AM 1.717mR 71.SuR/h 72.3uR/h 70.6uR/h 0.4uR/h 001-00:00 001-00:00 100.0 10/10/98 00:00:00AM .10/11/98 00:00:00AM 1.716mR 71.5uR/h 72.4uR/h 70.5uR/h 0.4uR/h 001-00:00 001 00:00 100.0 10/11/98 00:00:00AM 10/12/98 00:00:00AM 1.717mR 71.5uR/h 72.5uR/h 70.8uR/h 0.3uR/h 001-00:00 001-00:00 100.0 10/12/98 00:00:00AM 10/13/98 00:00:00AM 1.719d 71.6uR/h 72.5uR/h 71.0uR/h 0.3uR/h 001-00:00 001-00:00 100.0 10/13/98 00:00:00AM 10/14/98 00:00:00AM 1.721mR 71.7uR/h 72.4uR/h 70.8uR/h 0.3uR/h 001-00:00 001-00:00 100.0 10/14/98 00:00:00AM 10/15/98 00:00:00AM 1.730mR 72.1uR/h 74.5uR/h 71.1uR/h 0.6uR/h 001-00:00 001-00:00 100.0 10/15/98 00:00:00AM 10/16/98 00:00:00AM 1.722d 71.8uR/h 74.2uR/h 70.9uR/h 0.5uR/h 001 00:00 001-00:00 100.0 10/16/98 00:00:00AM 10/17/98 00:00:00AM 1.731mR 72.1uR/h 74.6uR/h 71.1uR/h 0.8uR/h '001-00:00 001-00:00 100.0 10/17/98 00:00:00AM 10/18/98 00:00:00AM 1.732mR 72.2uR/h 75.6uR/h 70.9uR/h 0.9uR/h 001-00:00 001 00:00 100.0 10/18/98 00:00:00AM 10/19/98 00:00:00AM 1.722d 71.7uR/h 72.6uR/h 70.9uR/h 0.3uR/h 001 00:00 001 00:00 100.0 l 10/19/98 00:00:00AM 10/20/98 00:00:00AM 1.7152 71.4uR/h 72.SuR/h 70.6uR/h 0.4uR/h 001-00:00 001-00:00 100.0 10/20/98 00:00:00AM 10/21/98 00:00:00AM 1.715mR 71.5uR/h 72.4uR/h 70.6uR/h 0.4uR/h 001-00:00 001-00:00 100.0 10/21/98 00:00:00AM 10/22/98 00:00:00AM 1.711d 71.3uR/h 72.1uR/h 70.4uR/h 0.4uR/h 001-00:00 001 00:00 100.0 10/22/98 00:00:00AM 10/23/98 00:00:00AM 1.715mR 71.SuR/h 72.6uR/h 70.1uR/h 0.5uR/h 001-00:00 001-00:00 100.0 10/23/98 00:00:00AM 10/24/98 00:00:00AM - 1.7092 71.2uR/h 72.1uR/h 70.2uR/h 0.4uR/h 001-00:00 001 00:00 100.0 10/24/98 ~ 00:00:00AM 10/25/98 00:00:00AM 1.709mR 71.2uR/h 72.0uR/h 70.4uR/h 0.2uR/h 001-00:00 001 00:00 100.0 10/25/98 00:00:00AM 10/26/98 00:00:00AM 1.714 2 71.4uR/h 72.5uR/h 70.7uR/h 0.3uR/h 001-00:00 001-00:00 100.0 10/26/98 00:00:00AM 10/27/98 00:00:00AM 1.728mR 72.0uR/h 73.0uR/h 71.1uR/h 0.3uR/h 001-00:00 001 00:00 100.0 10/27/98 00:00:00AM 10/28/98 00:00:00AM 1.731mR 72.1uR/h 75.9uR/h 71.0uR/h 1.0uR/h 001 00:00 001 00:00 100.0 l 10/28/98 00:00:00AM 10/29/98 00:00:00AM 1.717mR 71.5uR/h 72.8uR/h 70.6uR/h '0.SuR/h 001-00:00' 001-00:00 100.0 10/29/98 00:00:00AM 10/30/98 00:00:00AM 1.720mR 71.7uR/h 74.2uR/h 70.8uR/h 0.6uR/h 001-00:00 001-00:00 100.0 10/30/98 00:00:00AM 10/31/98 00:00:00AM 1.711mR 71.3uR/h 72.1uR/h 70.7uR/h 0.2uR/h 001-00:00 001 00:00 100.0 10/31/98 00:00:00AM 11/01/98 00:00:00AM 1.710mR 71.3uR/h 72.0uR/h 70.8uR/h 0.2uR/h 001-00:00 001 00:00 100.0  !

10/01/98 00:00:00AM 11/01/98 00:00:00AM 53.31d 71.7uR/h 75.9uR/h 70.1uR/h 0.5uR/h 031-00:00 031-00:00 100.0 l l

4

Table 4. October 1998 Data Report for PIC No. 2 I

Start Start End End Ave. Dose Interval Interval Standard Interval Data  % j DCte Time Date Time Oose Rate Max Min Dev. Time Recovered Recovered 1 10/01/98 00:00:00AM 10/02/98 00:00:00AM 1.651mR 68.8uR/h 69.7uR/h 67.9uR/h 0.3uR/h 001-00:00 001 00:00 100.0 10/02/98 00:00:00AM 10/03/98 00:00:00AM 1.653d 68.9uR/h 70.0uR/h 68.2uR/h 0.4uR/h 001 00:00 001 00:00 100.0 10/03/98 00:00:00AM 10/04/98 00:00:00AM 1.648mR 68.7uR/h 69.8uR/h 67.8uR/h 0.3uR/h 001 00:00 001-00:00 100.0 10/04/98 00:00:00AM 10/05/98 00:00:00AM 1.647mR 68.6uR/h 70.2uR/h 67.8uR/h 0.3uR/h 001-00:00 001 00:00 100.0 10/05/98 00:00:00AM 10/06/98 00:00:00AM 1.662mR 69.2uR/h 70.8uR/h 68.4uR/h 0.6uR/h 001 00:00 001 00:00 100.0 10/06/98 00:00:00AM 10/07/98 00:00:00AM 1.652mR 68.8uR/h 69.2uR/h 68.4uR/h 0.2uR/h 001 00:00 001-00:00 100.0 10/07/98 00:00:00AM 10/08/98 00:00:00AM 1.6484 68.7uR/h 69.6uR/h 68.1uR/h 0.3uR/h 001-00:00 001 00:00 100.0 10/08/98 00:00:00AM 10/09/98 00:00:00AM 1.650d 68.8uR/h 70.0uR/h 67.8uR/h 0.5uR/h 001-00:00 001-00:00 100.0 10/09/98 00:00:0,0AM 10/10/98 00:00:00AM 1.648d 68.6uR/h 69.4uR/h 67.9uR/h 0.4uR/h 001-00:00 001-00:00 100.0  ;

10/90/98 00:00:00AM 10/11/98 00:00:00AM 1.647d 68.6uR/h 69.5uR/h 67.8uR/h 0.4uR/h 001-00:00 001-00:00 100.0 j 10/11/98 00:00:00AM 10/12/98 00:00:00AM 1.646mR 68.6uR/h 69.4uR/h 67.9uR/h 0.3uR/h 001-00:00 001-00:00 100.0 10/12/98 00:00:00AM 10/13/98 00:00:00AM 1.6464 68.6uR/h 69.1uR/h 68.1uR/h 0.2uR/h 001-00:00 001 00:00 100.0 10/13/98 00:00:00AM 10/14/98 00:00:00AM 1.649mR 68.7uR/h 69.2uR/h 68.1uR/h 0.2uR/h 001 00:00 001-00:00 100.0  !

10/14/98 00:00:00AM 10/15/98 00:00:00AM 1.657d 69.0uR/h 71.4uR/h 68.2uR/h 0.5uR/h 001-00:00 001-00:00 100.0 10/15/98 00:00:00AM 10/16/98 00:00:00AM 1.654mR 68.9uR/h 71.3uR/h 68.0uR/h 0.5uR/h 001 00:00 001 00:00 100.0 10/96/98 00:00:00AM 10/17/98 00:00:00AM 1.661mR 69.2uR/h 71.3uR/h 68.1uR/h 0.7uR/h 001 00:00 001-00:00 100.0 10/17/98 00:00:00AM 10/18/98 00:00:00AM 1.662mR 69.2uR/h 72.4uR/h 68.0uR/h 0.8uR/h 001-00:00 001 00:00 100.0

'$0/18/98 00:00:00AM 10/19/98 00:00:00AM 1.650mR 68. bur /h 69.5uR/h 68.0uR/h 0.3uR/h 001 00:00 001-00:00 100.0

$0/19/98 00:00:00AM 10/20/98 00:00:00AM 1.644d 68.5uR/h 69.2uR/h 67.6uR/h 0.4uR/h 001 00:00 001-00:00 100.0 10/20/98 00:00:00AM 10/21/98 00:00:00AM 1.646mR 68.6uR/h 69.5uR/h 67.9uR/h 0.3uR/h 001 00:00 001 00:00 100.0 10/21/98 00:00:00AM 10/22/98 00:00:00AM 1.643d 68.5uR/h 69.5uR/h 67.7uR/h 0.3uR/h 001 00:00 001 00:00 100.0 10/22/98 00:00:00AM 10/23/98 00:00:00AM 1.648mR 68.7uR/h 69.7uR/h 67.6uR/h 0.5uR/h 001 00:00 001-00:00 100.0 10/23/98 00:00:00AM 10/24/98 00:00:00AM 1.642mR 68.4uR/h 69.0uR/h 67.7uR/h 0.3uR/h 001-00:00 001 00:00 100.0 10/23/98 00:00:00AM 10/25/98 00:00:00AM 1.644mR 68.5uR/h 69.2uR/h 68.0uR/h 0.2uR/h 001-00:00 001 00:00 100.0 10/25/98 00:00:00AM 10/26/98 00:00:00AM 1.647mR 68.6uR/h 69.7uR/h 67.9uR/h 0.3uR/h 001 00:00 001 00:00 100.0 10/26/98 00:00:00AM 10/27/98 00:00:00AM 1.658mR 69.1uR/h 69.9uR/h 68.2uR/h 0.3uR/h 001 00:00 001-00:00 100.0 10/27/98 00:00:00AM 10/28/98 00:00:00AM 1.662mR 69.2uR/h 72.9uR/h 68.3uR/h 0.9uR/h 001 00:00 001-00:00 100.0  ;

90/28/98 00:00:00AM 10/29/98 00:00:00AM 1.650mR ' 68.7uR/h 69.8uR/h 67.9uR/h 0.4uR/h 001-00:00 001 00:00 100.0 l 10/29/98 00:00:00AM 10/30/98 00:00:00AM 1.652d 68.8uR/h 71.1uR/h 68.0uR/h 0.5uR/h 001-00:00 001 00:00 100.0 10/30/98 00:00:00AM 10/31/98 00:00:00AM 1.644mR 68.5uR/h 69.2uR/h 67.8uR/h 0.2uR/h 001-00:00 001-00:00 100.0 10/31/98 00:00:00AM 11/01/98 00:00:00AM 1.639mR 68.3uR/h 68.9uR/h 67.9uR/h 0.2uR/h 001 00:00 001 00:00 100.0 10/01/98 00:00:00AM 11/01/98 00:00:00AM 51.15mR 68.7uR/h 72.9uR/h 67.6uR/h 0.5uR/h 031-00:00 031 00:00 100.0 5

i.,. ,

- Analysis a vi Commtnts 4

4 This section is divided into gamma radiation and neutron and gamma projections.

Gamma Radiation l' Normal (expected) levels of ambient gamma radiation were observed around the Prairie Island Nuclear Generating Plant and ISFSI from July to October 1998. Additional i monitoring data on radioactivity levels in other media (air for example) are available in the i

annual MDH "E.4vironmental Radiation Data Report," issued in April 1998.

3 j All radiation levels recorded by MDH off site of the Prairie Island plant have been f consistent with natural background (no plant effect has been observed). This lack of effect is most easily observed by comparing control locations with off-site indicator locations (for

! example, the TLD at Hastings 12 miles from the plant show that levels are not significantly l different from levels at the NSP Training Center).

l l MDH TLD readings varied in tae Third Quarter of 1998 from a low of 11.6 mR per

! quarter to a high of 22.6 mR per quarter. The highest reading occurred inside the ISFSI berm and ir.dicates direct,line-of-sight radiation from the spent fuel. NSP TLD readings .

j (see Attachment A.) varied during the Third Quarter from 13.3 mR per quarter to 95.7 mR l per quarter. The NSP range is expected to be wider because it takes more measurements i than MDH (54 compared to 12) so that there is a greater chance of outlying data. These

variations are also due to differences in radioactivity in the soil, variations in height above the soil, differences in microclimates, di.ierences in distances to the casks, and inaccuracies j in the TLD. The hMhest readings differ because the NSP TLD are much closer to the j casks.

i j During October, PIC No. I readings varied from 70.1 to 75.9 m!cro R per hour; PIC No. 2

] rea: lings varied from 67.6 to 72.9 mAro R per hour. The normal range is about 60 to 80 micro R per hour.

l

.i i Neutron and Gamma Projectigig i

) As spent fuel casks were added in 1995,19% and 1997, neutron detection counts increased

! . proportiona lly ot the amount of spent fuel stored. MDH first noticed this ircrease in TLD

response in the fourth quarter of 1995; it can be seen in Figure 2 (Shultis report, Jul,- 15, i 1998). NSP was not monitoring for neutrons. i I

i . Pecause the energy spectrum of the spent fuel neutrons was not known to MDH, the TLD could not be properly calibrated; however, a rough estimate indicated that the neutron dese was higher than the NSP "Skyshine 11" computer model indicated. The "Skyshine II" model was used in the Safety Analysis Report, which is the technical basis for licensir.g l

. the onsite storage of spent fuel casks.

l MDH and NSP staff first met on the issue on June 11,1997. It was agreed that neutrons I were being recorded by the TLD, but that no dose could be inferred.  ;

1 6 l I

.__ _ _ . _ _ _ _ _ _ _ __ __. ~. . _ . _ . _ . . _ _ . _ _ ___

. . J 7

i Neutrons are rare in the outdoor environment. Because of the difficulty in measuring environmental neutrons both NSP and MDH decided that expert assistance was necessary l ,for measuring neutrons and in analyzing the results. NSP hired a consultant at the end of

1997, after discussions with MDH and the U.S. Nuclear Regulatory Commission, to explain the apparent differences between the dosimeter readings and the "Skyshine II" model. l j MDH agreed that NSP contract with Dr. Ken Shultis, Professor of Mechanical and Nuclear

Engir.eering at Kansas State University to consult on ISFSI neutrons.

Dr. Shuitis completed two reporS on his work : "MCNP Calculated Near-field Neutron

Doses Using a Refined Cask Model" June 1,1998 and " Neutron Skyshine Analysis for the i Northern States Power Company Prairie Island Independent Spent Fuel Storage

! Installation" July 15,1998. The Monte Carlo Neutron Program (MCNP) is more sophisticated and detailed than "Skyshine II." Unlike "Skyshine II," MCNP considered the air-ground interface, interactions in air, and the actual cask geo<netry. These reports

confirmed that the "Skyshine II" model used in the original Safety Analysis Report l

underestimated neutron dose to the nearest resident by a factor of about 100. They also l l found that the berm, which had been constructed as a requirement of the 1992 Certificate j of Need, had a negligible shielding effect on neutron doses beyond about 30 meters from the j edge of the ISFSI.

l Shultis's MCNP (Monte Carlo Neutron Program) model was tested by comparing its i predicted cask surface dose rates with those measured by NSP and MDH. Neutron density l Is much higher here and easier to measure. If the MCNP model is accurate here,it is

! expected to be accurate at larger distances (700 meters away where the nearest resident l

] lives).

i On May 24,1995, MDH measured 2.5 mrem of neutron radiation per hour on the side of I

cask #1, when it was initially placed on the ISFSI pad. According to Shultis, this value must he multiplied by the energy spectrum correction factor of 0.809, which yields 2.0 mrem per hour, because the neutron energies are different than those used for the instrument calibration. The MCNP model at that point estimates 2.8 mrem per hour.

Thus, the model is conservative (over predicts neutron dose) by 2.8/2.0 or by about 1.4 times.

In order to estimate the total neutron and gamma dose to the nearest resident, MDH staff j used tL essumptions listed below and then calculated a total dose:

1 According to Dr. Shultis, the neutron dose to the nearest resident is projected to be 0.052 mrem per year. This is assuming that the resident's house would be shielded with 4 inches of wood (see Figure 3--Shultis Table 9, June 15,1998).

NSP's 1990 Safety Analysis Report reported that the actual fuel stored in the casks had a lower burnup and longer decay time than the MCNP model assumed. Lower burnups and longer decay times mean less radioactivity resides inside the spent fuel casks. According te NSP, these corrections reduce the dose to 0.040 mrem I.er year.

This dose must be reduced by 1.4 times because the MCNP model has been shown to over predict the neutron dose by 1.4 times; this division yields a dose of 0.029 mrem per year.

7

Gamma dose estimates must be added to this neutron dose. According to the NSP Safety Analysis Report,24 casks result in an additional 0.008 mrem of dose to the nearest resident

,per year. Reducing this by 17/24ths yields 0.006 mrem per year for 17 casks (the number of casks allowed under Minnesota Statute section 116C.771).

Thus, with 17 casks present, the best estimate of gamma and neutron dose to the nearest ISFSI resident (700 meters away) is 0.029 + 0.006, or 0.035 mrem per year. This is below the requirement of 0.054 mrem per year, which is the limit stated in the PUC Certificate of Need.

2.5 j

] Neutron source strength (scaled) incremental dose ratio

~

1.5 -

l 1.0 -

2/95 3/95 4/95 1/96 2/96 3/96 4/96 1/97 Quarter and year Figure 10. Incrernental quarterly-dose ratio and end-of-quarter neutron source strength of fuel in storage at the Prairie Island ISFSt. Dose ratios are based on raw Pana. sonic 11odel 814 neutron rnea-surements reported by the Afinnesota Department of Health.

. Figure 2. Neutron Source. Strength and Incremental Dose Ratio (from Shultis July 15,1998 report) 8 e

[',. .

• l

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1 l

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1 1

1 I

1 I

Table 9. Neutron skyshine dose rates at 700 m from ISFSI ,

l facility as calculated with the Cask 5 MCNP model. Results are l shown with and without 4" of wood surrounding the dose point. -

l l Year No. Casks

"*I"' # *

• I*"#Y' No. Casks w/o wood w wood .

1997. 7 6.28 0.066 0.024 1999 12 10.39 0.109 0.039 l 2002 17 13.92 0.146 0.052 i

i '

1 t

l

. Figure 3. Neutron Dose Rates at 70C m From ISFSI l (from Shultis July 15,1998 report) 1 l

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M .o-a s d.9 d.co in c.u tw. . a if l ,

l . . ATTACHMENT A:

NSP GAMMA TLD RESULTS

! Selected pages from the Radiological Environmental Monitoring Program monthly progress report are attached which describe locations and quarterly doses for

. ISFSI TLDs  !

e Pralrie Island Indian CommuNty area TLDs j e Plant site boundary area TLDs e Plant"4 to 5 Mile" area TLDs, and l 6 Control TLD.

A total of seven (7) loaded casks are in the ISFSI. Loaded casks were placed on the ISFSI pad:

l

. May 24,1995 e November 13,1995  ;

l December 21,1995 l

• May 30,1996 l e October 22,19c6 -

e January 12,1997, and e January 24,1997.

! The ISF51 TLDs inside the earth berm, which are in a direct line-of-sight from the casks, i show expected increases above the natural ambient dose.

l l

The ISFSI TLDs outside the earth berrn closest to the facility are showing a slight

[- increase in gamma radiation. The TLD with largest previous 4-quarter average is 3.8 millirem /qtr greater than the Control TLD's previous 4-quarter average. Models used to license the casks (Safety Analysis ~ Report Table 7A-7, Total Skyshine Dose Rate) i predict an expected dose rate of about 5 to 9 millirem /qtr higher than the natural amblent dose rates at these locations. Thus,if these TLD dose rates are indication of gamma skyshine from the casks, they are consistent with the Safety Analysis Report.

l The TLDs on the S!te Boundary and at the special Indian Community locations (P-07S f

& P-08S) remain at natural ambient lovels.

Page 1'of 6

Fnn no.

NOV-18-1998 WED 08:55 FM ,. , u a , .

ATTACHMENT 2 '

ISFSI TLD RESULTS f

• PRAIRIE 1SLAhV

. Tab!e 1. Ambient gamma radiation as measured by thermoluminescent dosimeters (TLD's).

Previous mR/91 days _

Cumulative Annual 2nd. Qtr. 3rd. Qtr. 4th. Qtr. Average Average 1.ocation ist. Qtr.

indientors(Inner Rine General Area of Site Boundarv) 16.0

• 0.2 15.4

• 0.2 15.1 12.6 P 01A 13.8 i 0.2 16.5 i 0.2 15.7 i 0.2 15.6 13.4

P 02A 14.5 i 0.2 .

16.9 i 0.2 17.110.3 16.3 13.7 P 03A 14.9 i 0 2 16.1

• 0.2 16.3

• 0.2 15.9 13.1 1 P-04A 15 3 i 0.2 16.1 i 0.2 16.4 i 0.2 15.9 13.7 l P-05A 153

• 0.2 16.1

• 0.2 16.8

• 0.2 16.0 13.0 i P-06A 15.1 0.2 16.7 i 0.2 16.310.2 15.8 14.2 i P07A 14.4 i 0.2 16.2

• 0.2 16.0

• 0.2 15.6 14.1 F-08A 14.6 t 02 16.21 0.3 163

• 0.2 15.8 14.6 P 09A 14.9

• 0.2 14.9

• 0.2 15.2

• 0.2 14.7 12.5 P-10A 14.1 i 0.2 ._

16.2 i 0.5 16.210.6 15.7 13.5 Mean i s.d. 14.7 i 0.5 Indicators (Outer Ring. 4-5 Miten Didant)

~

16.0 i 0.2 17.4 t 0.2 17.2 i 0.2 16.9 15 3

' P-01B 15.9 i 0.2 19.7 i 0.2 17.0 i 03 17.5 15.8 P-02B 18.2 i 0.4 18.8 i 0.2 18.1 17.0 P-03B 17.2 i 0.2 i 19.7 i 0.2 183 i 0.2 18.0 16.1 P 04B 16.0 i 0.2 15.6 i 0.2 15.2 0.2 15.0 14.0 P 05B 14.1 i 0.2 16.010.2 15310.2 15.0 13 3 P 06B 13.8 i 0.2 18.0

• 0.4 16.9 i 0 3 16.8 15.0 P 07B 15.4 i 0.2 14.9

• 0.2 16.9 t 0.2 15.910.2 15.9 13.9 P-06B i 17.5 i t.2 17.0 i 0.2 19.4 i 0.2 16.0 15.8 P-09B 183 i 03 18.6 i 0.2 17.6 14.5 P-10B 15.8 i 0 3 17.9 i 0 3 0.2 17.7 15.0 P 118 16.1 t 03 19.1 20.5

• 0.2 ~183 t 0.2 18.4 15 3 P 12B 163 1 03 17.810.3 17.1 i 03 16.6 14.5 P 13B 14.9 i 0.2 15.520.2 0.2 15.6 14.2 l P-14B 14.810.2 16.4 15.6 i 0.2 17.9 i 0.2 16.7 0.2 16.7 14.9 P 15B 17.8 i 1.5 173 13 16.9 15.0 Mean t s.d. 15.6 i 1.0 Control 17.1 15.5 P.01C 16.0 0.3 18.2 t 0.4 17.1 0.4 Page 2 of 6

N0h-18-1998EED08:55PM FAX N0. P. ;0 ,

F..

ATTACHMENT 2 ISFSl TLD RESULTS f PRAIRIEISI.AND j

• Table 1. Ambient gamma radiation as measured by thermoluminescent dosimeters (TLD's),

~

j (continued).  ;

Previous  ;

i ,

mR/91 days Cumuluve Annual -l F 2nd. Qtr. 3rd. Qtr. 4th. Qtr. Average - Average 1.ocation ist. Qtr. l I

Indicatars (hel.1 Interest Arena) ,

6 13.7 i 0.2 13.8

• 0.2 14.5

• 0.2 14.0 12.7

. P 01S '

16.010.2 16.2

• 0.2 17.0

• 0 3 16.4 15.5 P42S 15.9 i 0 3 - 18.9

• 0.4 18.7 i 0.2 17.8 15.7 i P03S-153 i 0.2 18.6 i 0.3 17.2 i 0.3 17.0 15.9 1 P 04S -

12.2103 13.7 i 0.3 13.3

• 0.2 13.1 12.1 P 05S 13.8 't 0.2 14.8

• 0.2 14.1 12.5 .;

, P46S 13.8 i 0.2 P07S 14 9 i 0.2 15.6

• 0.2 16.0

• 0.2 153 14.3 j

. P48S 15.0

• 0.2 16.0

• 0.2 16.1 i 0.2 15.7 13.9

)

Mean is.d. 106i 13 15.8 i 2.1 16.0

• 1.7 153 14.1 J' . ISFSI Area Inside Earth Berm

'46.3 i 0.4 42.6 i 0.3 42.8 39.5 )

3 P-011A : 39.6 t 0.2 23.3 20.9 I I - P.021A 22.1 i 0.2 24.9 i 0.2 22.9 i 0.2 21.9 i 0.2 26.0

• 0.2 23.7

• 0.2 23.9 21.1 P.031A 50.9 i 0.9 63.4 i 0 3 55.4

• 0.3 56.6 51.2 j P-041A 75.6 i 0.2 92.5 i 0.4 76.4 i 0.2 81.5 76.0 1 P 051A 26.7 i 0.2 30.2 t 0.3 27.8

• 0.2 28.2 25.2 -

P-061A 27.0 i 0.2 31.1

• 0.2 28.5 i 0.3 28.9 25.3 i P 071A 75 3 i 0.2 83.3 i 0.5 73.2 i 0.2 77.3 71.4 P.061A 95.7 i 0.2 101.6 0.4 89.8 i 0.3 95.7 88.8 P01IX 25.1 i 0.2 26.2

• 0.2 2L6 i 0.3 25.3 22.6 P 02IX P-03IX 94.9 i 0.7 99.010.2 95.7 i 0.3 96.5 91.4 P 0GX 20.9 i 0.2 21.6 i 0.2 21.0 03 21.2 19.2 i l

48.0129.5 53.8

• 32.1 48.5

• 283 50.1 46.1 l Meanis.d.

ISFSI Area Outaide Earth Berm ,

19.8 i 0.2 19.8 i 0.2 19.6 17.7 P-0118 19.110.2 i 19.8

• 0.2 20.1 i 0.2 19.9 19.4 l P42IB 19.7 t 0.3 21A i 03 20.2

• 0.2 20.6 18.0  !

P43IS 19.9 i 0.3 182

• 0.4 163 i 0.3 17.0 15.7 P44IB 16.0 i 0.2 17.6

• 0.2 17.0 i 0.2 16.9 15 3 P45IB 16.0 i 0.4 17.0 i 0.2 16.010.2 16.1 14.5 P46TB 15.3 i 0.2 17.0 t 0.2 17.1 i 0.2 16.7 14 6 P47IB 16.0 i 0 3 19.8 t 0.2 19.820.3 19.6 17.3 P4815 19.1 i 0.2 18.9 t 1.7 18.4 i 1.8 18.3 16.5 Mean s.d. 17.612.0 l Page 3 of 6 1

.. . .-. - - l

"k , NO M 8-1998 WED 08:55 FM Fnx No. ,, ,,

. ATTACHMENT 2 ISFSI TLD RESULTS Table D-2. Sampling locations, Prairie Island Nuclear Generating Plant,1998 (continued).

Dstance and Type of Direction from Code Type' Collection Site Sample' Renetor Ann nrimatelv d to 5 miles Distant from the Plant F 01S Thomas Killian Residence TLD 4.7 mi @ 355"/N Roy Kinneman Residence TLD 4.6 mig 17/NNE P 02B P-035 Wayne AndersonFarm TLD 4.9 mi G 46*/NE

, P 045 Nelson Drive (Road) TLD 4.2 mi O 61'/ ENE P-058 , Country Road E and Coulee TLD 4.1 ml @ 102d/ESE P-068 William Hauschibit Residence TLD 4.4 mi O 112*/ESE P 07B Red Wing PublicWorks TLD 4.7 mi G 140*/SE P-085 David Wnuk Residence TLD 4.1 ml 0165*/SSE P-098 Highway 19 South 1LD 4.2 mi GIST /S P-10B Cannondale Farm RD 4.9 mi 8 200"/SSW P 11B Wallace Weberg Farm TLD 4.5 mi @ M1'/SW P 125 Ray Cergen Farm RD 4.6 mi 0 251"/WSW P 138 Thomas O'Rourke Farm

• TLD L4 mi G 270*/W -

P-14B David }. Anderson Farm TLD 4.9 mi O 306'/NW P 15B Holst Farms TLD 3.6 mi @ 345'/hWW Seeciniinterest f nentiems

)

P-015 FederalLock & Dam #3 llD 1.6 mi @ 129'/SE  !

P-025 Charles Suter Residence TLD 0.5 mi@ 155'/SSE P-03f CarlCuatafson Farm TLD 2.2 mi 0173'/S l P-04S Richard Bun Residence TLD 2.0 mi G 202*/SSW P45S Kinney Store ED 2.0 mi @ 270*/W l EarlFlynnFarm TLD 2.5 mig 299'/WhW l P 06S P-07S Indian Community ~LD 0.7 mi G 271'/W l i

P-08S Irvilan Community TLD 0.7 mi O 2ST/NwW F-01C C Robertlunneman Farm TLD 111 mi G 331*/NNW l i

Page 4 of 6 e

~

Nb-18-1998Ld06:56PM F M 0. F. i  !

. . i ATTACHMENT 2 l l ISFSI TLD RESULTS l Table D 2. Sampling locations, Prairie Island Nuclear Generating Plant.1998 (continued).

, Approximate Type of Distance and Direction Code Type' Collection Site Sample' from ISFSI Center.

l 1CFS1 Area Imida Earth Berm P-011A ISFSINuisance Fence TLD 190' G 45'/NE P-021A ISFS! Nuisance Fence RD 360' @ S2"/E P 03!A ISFSI Nuisance Fence RD 370' @ 100'/E l , P 041A ISFSI Nuisance Fence 'ILD 200' O 134*/SE P-051A , ISFSINuisanceFence RD 160' O 219*/SW

P-061A ISFSI Nuisance Fence TLD 320' e 258*/WSW RD P 071A ISFS! Nuisance Fence 320' G 281*/WNW P 0SIA ISFSINuisance Fence TLD 190' @ 31r/NW P-01IX ISFSINulsance Fence TLD 140 @ 180*/S P-021X ISFSI Nuisance Fence RD 310' @ 270'/W P 03IX . ISFSI Nuisance Fence RD 140' @ 0*/N l

P411X ISFSI Nuisance Fence RD 360 G 90'/E

! ISFSI Area Outside Earth brm P-011B ISFSI Berm Area TLD 340' O 3*/N i F-021B ISFSIBerm Area TLD 380 @ 28'/NNE ,

P-03fB ISFSIBerm Area TLD 560' @ 85'/E l P-04IB ISFSI Berm Area RD 590' @ l65*/SSE l

P-05IB ISFSI Berm Area TLD 690' C 186'/S l P-06IB ISFSI Berm Area TLD 720' @ 201'/SSW

P-071B ISFSIBerm Area TLD 610' e 271'/W

! P-081B ISFS!3erm Area *ILD 360' @ 337*/NNW l

• "C" denotes controllocation. All other locations are indicators.

• Sample Codes:

AP = Airbome particulates WW = Well water i AI= Airbomelodine BS = Bottom sediment M = Milk SS = Shoreline sediment VE = Vegetation / vegetables BO = Bottom organisms (periphyton DW = Drinking water or macroinvertebrates)

! RW = River water F= Fish

! ' Distance and direction data for ik and bottom orgarlsms are approximate since availability of ,

sample specimen may vary at any nne location.

1 d

Page 5 of 6 ,

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